Weird film on my sons tongue.

Hey my son is 2 and a 1/2 his on antibiotics for a general bacterial infection were thinking UTI but it was unconfirmed because we couldn't get a urine sample. But he now has a weird film on his tongue and I'm wondering is it possible for him to get thrush from being on antibiotics? I didn't notice it before I noticed the tongue thing but his appetite is changing a little bit and hes referring some foods over others and I'm thinking maybe some foods are hurting his tongue. Was literally just out of work for 3 days straight so I don't wanna take him to the doctor quite yet I know there are some home remedies for thrush I tried brushing is tongue it doesn't come off so I'm pretty sure it's thrush and not mouth yucky stuff.

No picture, but its light tan/white and completely covers the far back of his tongue by his throat and gets clear as it moves towards the tip.